Purifier

ABSTRACT

In a system having a component  106  which is capable of reacting with a gaseous contaminant in a gas stream, a purifier assembly  102  is positionable in the gas stream and comprises a purifier medium  112  that reacts with the gaseous contaminant in a manner in which is substantially similar to the manner in which the component  106  reacts with the gaseous contaminant.

TECHNICAL FIELD

The present invention relates to devices and methods for purifying gasstreams. More particularly, the present invention relates to devices andmethods for removing contaminants, including gaseous contaminants, fromgas streams.

BACKGROUND OF THE INVENTION

In many industries, a high purity gas stream is used in a system formanufacturing a product. These systems may include a variety ofcomponents, including tubing, valves, orifices, and sensors, such asflow sensors, pressure sensors and temperature sensors. For example, inthe semiconductor industry, a high purity nitrogen gas stream may beused in a system for manufacturing silicon wafers. The system mayinclude an oxygen sensor for monitoring the amount of oxygen in thenitrogen gas stream, and the oxygen sensor may be made of a platinummetal.

Unfortunately, the high purity gas stream frequently contains gaseouscontaminants which can adversely react, chemically or physically, withthe components of the system. Although the source of these gaseouscontaminants may be external to the system, in many instances thegaseous contaminants are generated within the system itself, e.g.,during the process of manufacturing the product. For example, SiO₂ andother gaseous contaminants may be generated during the process formanufacturing the silicon wafers. These gaseous contaminants may beswept into the nitrogen gas stream and carried to the oxygen sensor. Theplatinum metal in the oxygen sensor reacts with the gaseous contaminantsin the gas stream, damaging the oxygen sensor. This and other types ofadverse reactions can occur with many components in many differentsystems, and damaged components can seriously degrade the reliability ofthe products produced by any system. Consequently, the components ofthese systems are subject to constant recalibration, extensivepreventive maintenance, and frequent premature failure, which result infrequent shut downs that substantially reduce the efficiency of thesystems.

SUMMARY OF THE INVENTION

Embodiments of the present invention may address one or more of thepreviously described problems as well as many other problems associatedwith contaminants in gas streams.

In accordance with one aspect of the invention, a purifier assembly maybe used in a system which has a component that is capable of reactingwith a gaseous contaminant in a gas stream. The purifier assembly may bepositioned in the gas stream upstream of the component, and the purifierassembly may comprise a bed of particulate material or a mass of fibrousmaterial. The material of the purifier medium is selected to react withthe gaseous contaminant in a manner which is substantially similar tothe manner in which the component reacts with the gaseous contaminant,thereby reducing or even eliminating the gaseous contaminant in the gasstream.

In accordance with another aspect of the invention, a purifier may beused in a system which has a component that is capable of reacting witha gaseous contaminant in a gas stream. The purifier may be positioned inthe gas stream upstream of the component, and the purifier may comprisea filter and a purifier medium. The filter removes particle contaminantsfrom the gas stream. The purifier medium is positioned in the gas streamdiscrete from the filter. The purifier medium includes a material whichis selected to react with the gaseous contaminant in a manner which issubstantially similar to the manner in which the component reacts withthe gaseous contaminant, thereby reducing or even eliminating thegaseous contaminant from the gas stream.

In accordance with another aspect of the invention, a purifier assemblyfor purifying a gas stream may comprise a purifier medium. The purifiermedium may include a bed of particulate material or a mass of fibrousmaterial, and the material has at least a metal surface. The metal ofthe purifier medium may be iron, ruthenium, osmium, cobalt, rhodium,iridium, nickel, palladium, platinum, copper, silver, gold, zinc,vanadium, and chromium and mixtures thereof.

In accordance with another aspect of the invention, a purifier forremoving contaminants from a gas stream may comprise a housing, apurifier assembly, and a filter. The housing may have an inlet and anoutlet and define a gas flow path between the inlet and the outlet. Thepurifier assembly may be disposed in the housing in the gas flow pathdiscrete from the filter. The purifier assembly may include a purifiermedium having a metal surface which is capable of reacting with gaseouscontaminants in the gas stream. The filter is disposed in the housing inthe gas flow path and removes particle contaminants from the gas stream.

In accordance with another aspect of the invention, a method ofprotecting a component capable of reacting with a gaseous contaminant ina gas stream comprises passing the gas stream through a purifier mediumbefore the gas stream is directed past the component. Passing the gasstream through the purifier medium includes passing the gas streamthrough a bed of particulate or a mass of fibrous material that reactswith the gaseous contaminants in a manner substantially similar to themanner in which the component reacts with gaseous contaminants, therebyreducing or even eliminating gases components from the gas stream.

Devices and method embodying the invention may include one or more ofthese various aspects of the invention. Embodiments which feature apurifier medium having a material or a metal surface that reacts withthe gaseous contaminants in the gas stream protect components of thesystem very effectively. The purifier medium may be located upstream ofthe component, so the gaseous contaminants react with the purifiermedium first. In reacting with the gaseous contaminants, the purifiermedium may pull the gaseous contaminants out of the gas stream orotherwise render the gaseous contaminants incapable of damaging thecomponent. Consequently, a highly purified gas stream continues past thepurifier medium and past the component without causing any damage to thecomponent.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of one example of a purifier in asystem with a component.

DESCRIPTION OF EMBODIMENTS

Devices and methods which purify gas streams in accordance with theinvention may be used to protect one or more components of a system fromgaseous contaminants in a gas stream. Any component of a system incontact with the gas stream may be protected, including, for example,tubing walls, valves, orifices, sensors, and transducers. The gas streammay comprise, for example, any process gas, including high purityprocess gases such as nitrogen, argon, hydrogen, and helium. The gaseouscontaminants may include a wide variety of gases, including, forexample, organometalic compounds such as arsine, phosphine, and siliconcontaining gases, e.g., SiO₂. Other gaseous contaminants may includecarbon dioxide and hydrocarbons.

The component may adversely react to the gaseous contaminants in a widevariety of ways, both physically and chemically. For example, thegaseous contaminant may plate, condense, coalesce, adsorb, absorb orotherwise be deposited onto one or more materials of the component inthe gas stream. Alternatively or additionally, the gaseous contaminantmay oxidize, reduce, form a complex with, or catalyze a reaction withthe material of the component. A purifier embodying the invention may beoperatively associated with the component, e.g., by inserting thepurifier in the gas stream upstream of the component. In preferredembodiments, the purifier may include a purifier medium that will beaffected by the gaseous contaminant in much the same way that thematerial of the component being protected would otherwise be affected,thereby sacrificially protecting the component. For example, thepurifier medium may react with a gaseous contaminant in a mannersubstantially similar to the manner in which the component wouldotherwise react to the gaseous contaminant, thereby pulling the gaseouscontaminant from the gas stream or otherwise rendering the gaseouscontaminant incapable of damaging the component, for example, byaltering the physical or chemical properties of the gaseous contaminant.

Purifiers embodying the invention may be configured in a wide variety ofways. One example of a purifier 100 is shown in cross section of FIG. 1.Generally, the purifier 100 may include a housing 101 and a purifierassembly 102 operatively associated with the housing 101. The housingmay be formed from any suitably impervious material which is compatiblewith the gas stream, including, for example, a polymeric material or ametal such as stainless steel. The housing 100 preferably includes atleast one inlet 103 and at least one outlet 104 and defines a gas flowpath between the inlet 103 and the outlet 104. However, the housing isnot limited to any particular shape. For example, the housing may bedesigned as a top mount assembly or a T-type assembly for themicroelectronics industry and may include both the inlet and the outleton the same end of the housing. In the illustrated embodiment, thehousing 101 may be designed as in-line assembly having a cylindricalconfiguration with the inlet 103 at one end and the outlet 104 at theopposite end. The inlet 103 and the outlet 104 may be configured asfittings and may be joined to corresponding fittings in a gas supplyline 105 which may fluidly communicate with the component 106 of thesystem to be protected. Further, the housing may comprise a one-piece ormulti-piece structure. For example, the housing may include a bodydefining a cavity for the purifier assembly and a head or basedetachably or permanently mounted to the body. In the illustratedembodiment, the housing 101 preferably comprises two hollow, generallycylindrical portions, e.g., an inlet portion 110 and an outlet portion111, which may be permanently coupled, e.g., bonded or welded.

The purifier assembly may be cooperatively arranged with the housing ina variety of ways. For example, the purifier assembly may be mounted tothe housing at the inlet and/or the outlet or within the housing. Thepurifier assembly may be the sole component within the housing, or thehousing may include the purifier assembly and one or more additionalcomponents, such as the component to be protected. For example, thepurifier assembly may be mounted near the inlet of the housing and thecomponent to be protected by the purifier assembly may be mounted insidethe housing between the inlet and the outlet. The purifier assembly maybe fitted to the housing in a variety of ways, for example, the purifierassembly may be removably mounted or permanently mounted to or in thehousing. The purifier assembly is preferably fitted to or in the housingcompletely across the gas flow path or the gas stream. However, thepurifier assembly may be disposed in the gas stream not completelyacross the gas stream but in sufficient contact with the gas stream toremove or otherwise render harmless a sufficient amount of the gaseouscontaminants to protect the downstream component. In the illustratedembodiment, the purifier assembly 102 is preferably disposed completelyacross the gas flow path defined by the housing 101 and permanentlyattached to the housing 101, e.g., by bonding or welding the purifierassembly 102 to the housing 101.

The purifier assembly may be variously configured. For example, thepurifier assembly may have a generally disc-shaped configuration or asolid generally cylindrical configuration through which the gas streammay pass axially. As another example, the purifier may have a hollowgenerally cylindrical configuration through which the gas stream maypass radially inside-out or outside-in. As yet another example, thepurifier assembly may have a generally cup-shaped configuration. Thecross section of any of these configurations may be regular, e.g.,circular or polygonal, or may be irregular. In the illustratedembodiment, the purifier assembly 102 preferably has a generallydisc-shaped configuration with a generally circular cross section.Further, the purifier assembly may be configured as a single piecestructure or a multi-piece structure. The purifier assembly preferablycomprises one or more purifier media and may comprise additionalstructures for supporting the one or more purifier media, for example,within the housing. In the illustrated embodiment, the purificationassembly 102 includes a purifier medium 112 contained by an annular ringor spool 113 and upstream and downstream porous barriers 114, 115.However, the supporting structures may vary widely from one purifierassembly to another depending, for example, on the nature of thepurifier medium. In some embodiments, the housing may support thepurifier medium without any additional supporting structures.

The purifier medium preferably comprises a material that will beaffected by gaseous contaminants in the gas stream in a mannersubstantially similar to the way in which the material of the componentbeing protected would otherwise be affected by the gaseous contaminants.Thus, the material of the purifier medium may be identical to thematerial of the component being protected or analogous to the materialof the component being protected, i.e., capable of reacting to thegaseous component in a substantially similar manner. Two or morepurifier media may be included, for example, where different componentswithin the system are to be protected. For many embodiments, thematerial of the purifier medium preferably comprises a metal, mostlyincluding, for example, noble metals and Group VIII metals. Morepreferably, the metal of the purification medium may comprise one ormore of the following metals: iron, ruthenium, osmium, cobalt, rhodium,iridium, nickel, palladium, platinum, copper, silver, gold, zinc,vanadium, and chromium and mixtures of these metals. The material of thepurification medium may include only a single constituent, e.g., asingle metal, or may be combined with various other constituents,including additional metals and/or non-metals such as sorbents andcatalysts.

The purification medium may comprise any suitable form. For example, thepurification medium 112 may be in the form of one or more masses offibrous material, such as a mat, a gauze, a wool, a non-woven web, or amesh, e.g., a woven web, in one or more layers. The fibers of thefibrous material have any suitable diameter, e.g., several thousands ofan inch or less, and any suitable length, e.g., several inches or less.The fibers may be a substantially pure form of the purifier materialselected to react with the gaseous contaminants. For example, each fibermay entirely consist of a metal. Alternatively, each fiber may comprisea combination of the selected purifier material and one or more othermaterials. Preferably, however, the fiber at least includes the selectedpurifier material as a surface which may be contacted by the gas stream.For example, each fiber may comprise a metal, ceramic, or polymeric basematerial coated with the selected purifier material in any suitablemanner. The mass of fibrous material is preferably compressed to providea uniform density. Even more preferably, the mass of fibrous materialmay be fashioned as a preform, e.g., a fibrous structure havingpredetermined dimensions, and the preform may have any suitableconfiguration such as a disc-shaped configuration or a cylindricallyshaped configuration.

Alternatively, the purification medium 112 may comprise one or more bedsof particulate material. The particulate material may be beaded,granular, or powdery, and the individual particles may have variousregular or irregular shapes including dendritic, acicular, fibril, andspherical. The particles may be a substantially pure form of thepurifier material selected to react with the gaseous contaminants. Forexample, each particle may entirely consist of a metal. Alternatively,each particle may comprise a combination of the selected purifiermaterial and one or more other materials. Preferably, however, theparticle at least includes the selected material as a surface which maybe contacted by the gas stream. For example, the particles may comprisea metal, ceramic, or polymeric base material coated with the selectedpurifier material in any suitable manner. The nominal size and amount ofthe particulate material and the size of the particulate bed may varywidely, depending on such factors as the desired capacity and efficiencyof the bed and the desired flow parameters, e.g., pressure drop and flowrate, through the bed. In some embodiments, size of the particulatematerial may be less than about 1/20th of the lateral dimension, e.g.,diameter, of the particulate bed, more preferably less than about1/100th of the lateral dimension. Further, the bed of particulatematerial may be immobilized, for example, by a binder or in a fibrousmatrix or by sinter bonding the particles to one another and/or asubstrate. Preferably, the particles of the bed are not bonded to oneanother but are packed within the bed sufficiently tightly to preventthe bed from fluidizing and/or forming channels in the bed as the gasstream flows through the bed. The bed of particulate material maycompletely fill the housing, or the particulate material may occupy lessthan the internal volume of the housing.

In the illustrated embodiment, the purifier medium 112 preferablycomprises a bed of particulate material which may be radially containedwithin the annular ring 113. For example, the purification medium 112may comprise a bed of particulate material tightly packed within theannular ring 113. The inner diameter of the annular ring may be greaterthan the inner diameter of the housing but is preferably substantiallyequal to or, even more preferably, somewhat less than the inner diameterof the housing 101. The thickness and the inner diameter of the annularring 113 may vary depending on factors such as the amount and size ofthe particulate material to be contained within the bed. For example,the bed of particulate material may have a diameter of about 0.75 inchor less, e.g., about 0.50 inch or less, and a thickness of about 0.250inch or less, e.g., about 0.125 inch or less, and the bed may containabout 3 grams or less, e.g., about 2 grams or less, of metal particleshaving a size of about 100μ or less, e.g., in the range from about 10μto about 45μ. For embodiments intended to protect an oxygen sensorhaving a platinum surface in the gas stream, particles of platinummetal, such as those available from Alfa Aesar, A Johnson MattheyCompany of Ward Hill, Mass., may be selected for the purifier material.

The porous barriers 114, 115 are preferably disposed on both sides ofthe bed to axially contain particulate material within the bed. Theporous barriers may be bonded, e.g., welded along their edges, andcompletely contain the bed of particulate material without significantadditional structure. In the illustrated embodiment, the porous barriersare cooperatively arranged with additional supporting structure, such asthe annular ring 113, to contain the bed of particulate material, e.g.,within the interior of the annular ring 113. The size of the openings inthe porous barrier 114, 115 depends on the size of the particulatematerial in the bed, finer particulate material indicating smalleropenings in the porous barrier. The porous barrier may comprise anysuitably porous structure such as a fibrous web, a mesh, a porousmembrane or a porous composite material, and may be formed from anysuitable material such as metal or polymer. In the illustratedembodiment, the upstream porous barrier 114 preferably comprises aporous composite material including a layer of PMF™ 316L stainless steelporous medium sandwiched between layers of sintered Rigimesh® (Grade K)porous medium having a composite gaseous removal efficiency of about10e2 at 0.4 microns.

The downstream porous barrier 115 may be identical or similar to theupstream porous barrier 114. However, in many embodiments, thedownstream porous barrier may comprise a high efficiency filter having agaseous removal efficiency, for example, on the order of 10e4, morepreferably on the order of 10e6, and even more preferably on the orderof 10e9, for 3 nanometer particles. A high efficiency filter isavailable from Pall Corporation under the trade designation MiniULTRAMET-L™ 1100 Series Assembly. A high efficiency filter not onlyserves to contain the particles of purification material within the bed,it also removes solid contaminants from the gas stream. While thepurifier medium 112 is preferably located upstream of the highefficiency filter, it may be located downstream of the high efficiencyfilter or it may be sandwiched between portions of the high efficiencyfilter. However, in preferred embodiments, the purifier medium, whetherupstream, downstream or within the high efficiency filter, is disposedin the gas stream discrete from the high efficiency filter, e.g., thepurifier medium and the filter are preferably positioned at discretelocations within the gas stream. Combining the purifier medium with thehigh efficiency filter, e.g., by coating the high efficiency filter withthe selected purification material, may result in design trade offs anddegraded performance.

The purifier may be fabricated in a wide variety of ways depending, forexample, on the desired configuration of the purifier and the nature ofthe purifier medium. For example, in the illustrated embodiment, thedownstream porous barrier 115, e.g., the high efficiency filter may bejoined between the open end of the outlet portion 111 of the housing 101and a rim of the annular ring 113. These components are preferablyjoined by a bond, e.g., an adhesive or solvent bond, or, morepreferably, a weld, which seals them to one another, seals the outeredge of the downstream porous barrier 115, and forces the downstreambarrier 115 tightly against the face of the annular ring 113, defining apocket between the downstream porous barrier 115 and the wall of theannular ring 113.

The purifier medium 112 may be selected in accordance with the materialof a component to be protected and then positioned in the pocket. Forexample, a mass of fibrous material selected in accordance with thecomponent being protected may be positioned in the pocket. Inparticular, a preform of the fibrous mass having dimensionscorresponding to, e.g., slightly larger than, the dimensions of thepocket may be inserted in the pocket, preferably, with a interferencefit between the edge of the preform and the inner wall of the annularring. Alternatively, a bed of particulate material selected inaccordance with the component to be protected may be deposited withinthe pocket. The particular material may be wet laid in the pocket on thedownstream porous barrier 115 but is preferably dry laid in any suitablemanner. For example, an amount of the selected particulate material maybe dry laid in the pocket and compacted, e.g., by vibrations and/orforce, to pack the bed. An additional amount of selected particulatematerial may then again be dry laid and compressed, and this process maycontinue until the pocket is filled or, more preferably, slightlyoverfilled, with a packed bed of selected particulate material.

Once the purifier medium has been disposed in the pocket of the annularring 113, the upstream porous barrier 114 may be joined between the openend of the inlet portion 110 of the housing 101 and the opposite rim ofthe annular ring 113. Again, these components are preferably joined by abond or a weld which seals them to one another, seals the outer edge ofthe upstream porous barrier 114, and forces the upstream porous barrier114 tightly against the face of the annular ring 113, tightly confiningthe purifier medium 112 within the pocket of the annular ring 113.

Once the purifier is fabricated, it may be positioned in the gas streamupstream from the component 106 to be protected, for example, byinserting the purifier into the gas supply line 105. The gas streampasses along the gas supply line 105 through the purifier 100, and asubstantial portion of, preferably all of, the gas in the gas streamcontacts, e.g., passes through, the purifier medium 112. The gaseouscontaminants in the gas stream react with the purifier medium 112 in amanner substantially similar to the manner in which the material of thecomponent 106 would otherwise react with the gaseous contaminants. Byreacting with the gaseous contaminants in a manner similar to that ofthe component 106, the purifier medium 112 may pull the gaseouscontaminants out of the gas stream, substantially reducing the amount ofgaseous contaminants in the gas stream and/or may otherwise render thegaseous contaminants incapable of harming the component 106, forexample, by chemically reacting with the gaseous contaminants andtransforming the gaseous contaminants into substances which are notharmful to the component 106.

From the purifier medium 112, the gas stream may pass through the highefficiency filter and then past the component 106. Because the gasstream has been purified by the purifier medium 112, the component 106remains unharmed by the gas stream. The component 106 thus functionsmore reliability for a much longer period of time, eliminating frequentshutdowns for recalibrating, maintaining and/or replacing a damagedcomponent. Consequently, the system operates much more efficiently andreliably.

While the invention has been described in some detail by way of variousembodiments, the invention is susceptible to various modifications andalternative forms and is not restricted to the specific embodimentspreviously described and illustrated. For example, a purifier assemblymay include both a mass of fibrous material and a bed of particulatematerial, either separate or dispersed within one another. Further, inthe illustrated embodiment, the purifier assembly comprises a purifiermedium disposed across the gas flow path and spaced from the componentbeing protected. Alternatively, the purifier assembly may comprise anyother porous structure which includes the purification medium andencapsulates or otherwise covers the component and protects thecomponent from gaseous contaminants in the fluid stream. For example,the purifier assembly may comprise a porous jacket which is formed fromor coated with the material selected to protect the component. Thus, thespecific embodiments disclosed are not intended to limit the invention,but on the contrary the invention is intended to cover all modificationsequivalence and alternatives falling within the spirit and scope of theinventions defined by the following claims.

All references cited herein including publications, patents, and patentapplications, are hereby incorporated in there entireties by reference.

1. A purifier for removing contaminants from a gas stream, the purifiercomprising a housing having an inlet and an outlet and defining a gasflow path between the inlet and the outlet, a filter disposed in thehousing in the gas flow path to remove particle contaminants, and apurifier assembly cooperatively arranged within the housing in the gasflow path discrete from the filter, wherein the purifier assemblyincludes a purifier medium including a packed bed of unbonded metalparticulate material capable of reacting with a gaseous contaminant inthe gas stream, wherein the metal particulate material includes metalparticles having a size less than about 100 μ and wherein the metalparticles have a surface which is exposed to react with the contaminantsof the gas stream.
 2. The purifier of claim 1 wherein the purifierassembly is disposed in the housing.
 3. The purifier of claim 1 whereinthe purifier medium is positioned upstream of the filter.
 4. Thepurifier of claim 1 wherein the purifier medium comprises a bed ofparticulate metal, the metal being selected from the group consisting ofiron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium,platinum, copper, silver, gold, zinc, vanadium, and chromium andmixtures thereof and particles of the metal having a size less thanabout 100 μ.
 5. The purifier assembly of claim 1 wherein the filtercomprises a high efficiency filter.